1. Field of the Invention
This invention relates to thermally insulated building construction panels of the type formed by a pair of spaced apart metal skins and an interposed thermal insulation material which adhesively binds the metal skins together into a panel and more particularly to improved side-joint construction for assembling such panels into a wall.
2. Description of the Prior Art
Building construction panels having metal liner sheets, metal facing sheets and an interposed core of thermal insulation such as polyurethane foam are well known. A variety of connecting side joints for such construction panels has been proposed. Some of the side joints are designed to permit the fabrication of the building construction panel from identical metal facing sheets and liner sheets so that the panel fabricator requires only a single roll-former line or process to produce the matel facing sheets and liner sheets for the panel. It is also known to assemble building construction panels from liner sheets having different joint configuration profiles from the profiles of the facing sheets. The use of threaded fasteners, hidden from view, to secure such building construction panels to a building framework is commonplace. The use of supplemental metal clamping plates to retain the panels in position also is well known.
A principal shortcoming of the thermally insulated, double-skinned metal panels of the prior art is their unsatisfactory performance in fire tests. Frequently the panels are fabricated with polyurethane foam as the core material. While the combustability of polyurethane foam is well known, the thermal insulating character of such polyurethane foams is excellent. When the polyurethane foam is encapsulated within the metal skins of a double metal skin panel, the fire performance of the resulting panel is surprisingly good until that stage of the fire test where the panel joints spring open and allow the polyurethane foam to become exposed. The panels normally fail the fire tests at that stage. A panel joint which resits disengagement under stress will improve the panel fire rating.
Another difficulty with existing insulated double-skin panels is that the side joint has been the critical limiting strength component of a wall assembled from such panels. Hence the side joint has been a limiting consideration in establishing maximum panel width. By developing a stronger side joint construction which resists slippage and disengagement under stress, other panel parameters become controlling in width determination and wider panels can be successfully produced. Wider panels in general reduce construction costs and improve the fire endurance properties of the resulting panel wall by providing fewer joints over a wall surface.